1. Field of the Invention
The present invention relates to the field of computer systems and their operating systems, in particular, computer systems executing the UNIX.RTM. system (UNIX is a registered trademark of UNIX System Laboratories, Inc.). More specifically, the present invention relates to providing access to symbolic definitions in a dynamically configurable operating system, in particular, the kernel of a UNIX.RTM. system.
2. Background
Traditionally, many operating systems including the kernel of the UNIX.RTM. system are pre-built as one executable image, that is all program segments of the operating system are statically linked, resolving all symbolic references to the symbolic definitions. Typically, under this approach, a file containing a symbol table comprising entries of all symbolic definitions is available on disk for any utility or application program that needs access to the information.
While the pre-built single executable image operating system is often tailorable, special knowledge and skill are usually required. As a result, experience has shown that most computer systems simply use the generic version even though many functions included in the generic version are not used, thereby wasting memory resources.
Today, some operating systems including the kernel of some UNIX.RTM. systems are configured dynamically. Under a fully dynamically reconfigurable operating system, the functions offered by the operating system are distributed over a root executable segment and a number of relocatable segments. The root executable segment is loaded and given control during system startup. The functions distributed in the relocatable segment are dynamically loaded and linked on an as needed basis. In the event of memory constraint, some dynamically loaded and linked relocatable segments that have not been used recently may even be overlaid. As a result, the symbol definitions available at any particular point in time change dynamically. Thus, a new approach must be used to ensure the symbol definition information accessed by the utilities and the application programs are current and not stale.
As will be discussed, the present invention provides a method and apparatus for providing access to symbol definitions in a dynamically configurable operation system, in particular, a dynamically configurable kernel of the UNIX.RTM. system.
For further description of the UNIX.RTM. system including the kernel, see M. J. Bach, The Design of the UNIX.RTM. Operating System, Prentice Hall, 1986.